Mobile devices such as cellular telephones, wireless communication devices, laptop computers, handheld multimedia devices, tablet computers, etc., conventionally involve integration of various subsystems on a chip or integrated circuit. For example, mobile devices may include one or more components or subsystems such as, processing cores, antennae, transceivers, memory or storage elements, and user interfaces such as microphones, speakers, keypads, display systems, etc. These subsystems may be integrated on a single chip solution or packaged within close proximity of one another. The subsystems may operate under varying operating conditions such as operating voltage, frequency, temperature, etc. Sometimes interference or concurrency may arise due to conflicting operating conditions between two or more subsystems.
For example, frequency interference may arise between two or more components or subsystems of a mobile device. More specifically, a radio frequency subsystem may include a FM subsystem or FM transceiver, with a conventional operating frequency in the general range of 76 MHz to 108 MHz. While in general, processing cores operating at a much higher frequency of 1-2 GHz may not interfere with the FM subsystem, it may be possible for harmonics of the local oscillator (local clock) of the FM subsystem to mix down higher frequency components in the 1-2 GHz range, therefore potentially interfering with the FM frequency reception. Further, lower harmonic frequencies of operation of other subsystems may overlap with or interfere with the FM operating frequency. One component which may be of particular concern with regard to causing interference with the FM subsystem is a display subsystem.
A display subsystem may include, among various other components, a display driver and a display device such as a liquid crystal display (LCD). The display driver may control the operating frequency or clock for the display system. With conventional settings, it is possible that when the display subsystem is turned on (e.g., a mobile phone's display or display backlight is active or turned on), that the frequency of operation of the display subsystem may interfere with the FM subsystem. Accordingly, when the display subsystem is turned on, the FM subsystem may suffer from degraded performance due to noise arising from the interference. Performance degradation in the FM subsystem may be in the order of 10-15 dB, which may severely impact quality and user experience. Such interference between the FM subsystem and display subsystem is also referred to as a FM-display concurrency issue.
Conventional approaches to resolve the FM-display concurrency issue and mitigate the interference or noise caused by the display subsystem on the FM subsystem have involved complex layout design guidelines. Such layout guidelines may specify various requirements for ground isolation, shielding, and on-chip placement restrictions on the FM subsystem and the display subsystem. However, such approaches have limited success and they are not adaptable to process variations. For example, the carefully designed isolation and shielding at the time of manufacture may not be sufficient to prevent interference under operating conditions. With shrinking device sizes, there may be very limited flexibility to design the on-chip placement of the FM subsystem and display subsystem, such that they are sufficiently separated to effectively avoid or mitigate the concurrency issue. Moreover, layout and placement techniques tailored for the FM subsystem and the display subsystem may be limited in the context of designing the entire systems on a chip, because conflicting requirements may arise from the placement requirements of other components or subsystems on the chip.
Accordingly, there is a need in the art for overcoming the aforementioned limitations of conventional approaches with regard to the FM-display concurrency issue.